1. Field of the Invention
The present invention relates to a composite plating apparatus capable of giving a composite plating on the surfaces of various members, particularly on the inner surface of a cylinder formed in a hollow member, by loosely inserting an electrode into the cylinder to form an annular space, by flowing composite plating solution in a gap defined between the electrode and the inner surface of the cylinder and by applying a voltage between The electrode and the hollow member, and to an apparatus for dispersing a composite plating solution to the composite plating apparatus.
2. Description of the Related Art
Conventionally, in order to improve wear resistance of, for example, the inner surfaces of automobile engine cylinders, an apparatus has been known in which a composite plating solution comprised of a nickel sulfate solution having fine grains of silicon carbide dispersed therein is passed through the cylinder to deposit the nickel and silicon carbide on the inner surface of the cylinder.
In such an apparatus as described above, the inner surface of the cylinder is generally plated by inserting an electrode into the cylinder with a space or clearance, by connecting the cylinder to the base electrode and by introducing a composite plating solution in the space between the electrode and the cylinder.
In order to improve the deposition effect of the fine grains on the inner surface of the cylinder, a method has been known where air is fed into the composite plating solution to generate air bubbles therein and the air bubbles are mixed into the composite plating solution flowing in the space between the electrode and the cylinder so that the air bubbles press the fine grains onto the inner surface of the cylinder. However, when the air bubbles are mixed into the composite plating solution flowing in the space of the cylinder, deposition of fine grains differs from spot to spot on the inner surface of the cylinder unless the air bubbles are uniformly dispersed within the plating solution. As a result, consistent quality cannot be obtained.
In the conventional apparatus, as shown in FIG. 16, the electrode to be inserted into the cylinder is supported only at the base end portion thereof. Thus, the annular space defined between the electrode and the inner surface of the cylinder cannot be securely maintained, thereby depositing the plating with nonuniform thickness. On the other hand, when the tip end of an electrode 51 is engaged with an engaging portion 52a of an electrode engaging member 52 so as to support the electrode 51 at both ends thereof the space S defined between the inner surface of the cylinder W and the electrode 51 can be held constant. However, the flow direction (the direction shown by the arrows) of the plating solution changes near the inlet of the cylinder, thereby causing uneven suspension of fine grains of silicon carbide so that the deposition of nickel and silicon carbide become inconsistent.
In FIG. 16, there are shown holding jigs 53 and 54 for holding a cylinder block W and an electrode supporting plate 55 for supporting a base end portion of the insertion electrode.